A conventional technology described in Patent Document 1 relates to a vehicular air conditioner that includes a first air passage through which an air blown by a first fan flows, and a second air passage through which an air blown by a second fan flows. The first air passage and the second air passage are used as separated passages partitioned by a partitioning plate inside an air-conditioning casing. The conventional device includes an evaporator extending across both the first air passage and the second air passage, a heater core extending into both the first air passage and the second air passage at a downstream side of the evaporator, and air mix doors disposed in each of the first air passage and the second air passage between the evaporator and the heater core. In the conventional device, when an inside-outside air switching door is switched to be located at a predetermined position, and when the outside air is drawn by the first fan and the inside air is drawn by the second fan, the outside air flows through the first air passage and the inside air flows through the second air passage.